CMA Foundation · Fundamentals of Business Mathematics and Statistics · Indices and Logarithms
If 3^(x+1) = 81, then the value of 2^x is:
The value of 2^x is 8. Since 81 equals 3^4, equating exponents gives x + 1 = 4, so x = 3. Therefore 2^x = 2^3 = 8. Forgetting to subtract the one would give x = 4 and a wrong answer.
- A4
- B8Correct
- C16
- D6
Explanation
81 = 3^4, so x+1 = 4 and x = 3. Then 2^x = 2^3 = 8. The option 16 results from taking x = 4 and forgetting the +1.
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